Collaborative planning and prediction: Does group discussion affect optimistic biases in time estimation?

Intuition and previous research indicate that individuals commonly display an optimistic bias in time prediction. The present studies extend research on task completion forecasts to examine tasks performed collaboratively by groups, and predictions generated through group discussion. Participants predicted-individually and collaboratively-when they would complete upcoming group projects ranging from brief laboratory tasks to extensive real-world projects, and their actual completion times were measured. Results supported the three guiding hypotheses. First, there was an optimistic bias for both individual (Studies 1 and 2) and group predictions (Studies 1-3). Second, predictions generated through group discussion were more optimistic than those generated individually. Third, this “group accentuation” effect was mediated by the informational focus at the time of prediction. Group discussion heightened participants' tendency to focus primarily on factors promoting successful task completion, and this selective focus on “planning for success” enhanced their optimistic outlook. Discussion centers on theoretical contributions to the individual and group decision making literatures, as well as applied implications for planning and forecasting within organizational contexts.